Was DeepMind's DQN Atari game learning simultaneous?
Switching required a re-learn.

Also, note that:


  We use the same network architecture, learning
  algorithm and hyperparameters settings across all seven games, showing that our approach is robust
  enough to work on a variety of games without incorporating game-specific information. While we
  evaluated our agents on the real and unmodified games, we made one change to the reward structure
  of the games during training only.


and 


  the
  network has outperformed all previous RL algorithms on six of the seven games we have attempted
  and surpassed an expert human player on three of them.